Methods to Study Protein-Binding to Pseudogene Transcripts

The anticancer effects of Metformin in the male germ tumor SEM-1 cell line are mediated by HMGA1

INTRODUCTION

Germ cell tumors (GCTs) are the most common type of cancer in young men. These tumors usually originate from the testis, but they can occasionally develop from extragonadal sites probably due to primordial germ cells (PGCs) migration errors. Cisplatin-based chemotherapy is usually effective for male GCTs, but the risk of toxicity is high and new therapeutic strategies are needed. Although Metformin (Met) has been widely studied as a potential cancer treatment over the past decades, there is limited evidence to support its use in treating male GCTs. Additionally, the mechanism by which it acts on tumor cells is still not entirely understood.

METHODS

SEM-1 cells, a newly established human cell line of extragonadal origin, were treated with Met. Cell viability was studied by MTT assay, while cell migration and invasion were studied by the wound healing assay and the transwell assay, respectively. The effect of Met on 3D spheroid formation was determined by seeding SEM-1 cells in appropriate cell suspension culture conditions, and cell cycle was characterized by flow cytometry. Factors involved in PGCs migration and GCT invasion, such as IGFBP1, IGF1R, MMP-11 and c-Kit, together with cyclin D1 (a key regulator of cell cycle progression), and the upstream factor, HMGA1, were determined by immunoblots.

RESULTS

Treatment of SEM-1 cells with Met resulted in a potent and dose-dependent reduction of cell proliferation, as evidenced by decreased nuclear abundance of cyclin D1 and cell cycle arrest in G1 phase. Also, Met prevented the formation of 3D spheroids, and blocked cell migration and invasion by reducing the expression of IGFBP1, IGF1R and MMP-11. Both, IGFBP1 and MMP-11 are under control of HMGA1, a chromatin-associated protein that is involved in the regulation of important oncogenic, metabolic and embryological processes. Intriguingly, an early reduction in the nuclear abundance of HMGA1 occurred in SEM-1 cells treated with Met.

CONCLUSIONS

Our results document the antiproliferative and antimigratory effects of Met in SEM-1 cells, providing new insights into the potential treatments for male GCTs. The anticancer properties of Met in SEM-1 cells are likely related to its ability to interfere with HMGA1 and downstream targets, including cyclin D1, the IGFs system, and MMP-11.

Pseudogene fms-related tyrosine kinase 1 pseudogene 1 (FLT1P1) cooperates with RNA binding protein dyskeratosis congenita 1 (DKC1) to restrain trophoblast cell proliferation and angiogenesis by targeting fms-related tyrosine kinase 1 (FLT1) in preeclampsia

In preeclampsia (PE), preexistent maternal endothelial dysfunction leads to impaired placentation and vascular maladaptation. Long noncoding RNAs (lncRNAs) have been shown to participate in the placentation process. LncRNA fms-related tyrosine kinase 1 pseudogene 1 (FLT1P1) was previously reported to be upregulated in PE. In this study, we verified the effect of FLT1P1 and its cognate gene FLT1 on trophoblast cell proliferation and angiogenesis by using Cell Counting Kit-8 (CCK-8) assay, tube formation assay, and western blot analysis. Their binding to RNA binding protein dyskeratosis congenita 1 (DKC1) was validated by conducting RNA immunoprecipitation (RIP) and RNA pulldown assays. In this study, knockdown of FLT1P1 or FLT1 was found to promote cell proliferation and angiogenesis in trophoblasts. In addition, FLT1P1 recruited DKC1 to stabilize FLT1. Importantly, silencing FLT1P1 or DKC1 decreased the stability of FLT1. Rescue assays revealed that FLT1 overexpression reversed the effect of silenced FLT1P1. Overall, FLT1P1 cooperates with DKC1 to restrain trophoblast cell proliferation and angiogenesis by targeting FLT1.